1. Field of the Invention
This invention relates to a semiconductor manufacturing process and also to a semiconductor device. Specifically, the present invention is concerned with a semiconductor manufacturing process comprising a step for etching stacked films composed of a tungsten film and a titanium-base film and also with a semiconductor device manufactured by the same process.
2. Description of the Background Art
When electrons flow through a fine line metal pattern, the metal pattern may undergo deterioration due to electromigration. Known examples of metallic materials excellent in electromigration resistance include tungsten. Keeping in step with ever-increasing miniaturization of semiconductor devices in recent years, tungsten has found utility as a material for gate electrodes and bit lines owing to its higher electromigration resistance compared with polysilicon.
When tungsten is used as an interconnecting material in a semiconductor device, a tungsten film is formed over a titanium-base barrier metal. To pattern interconnections of such a construction with good accuracy, it is necessary to anisotropically etch the tungsten film and the titanium-base film at high selectivity.
However, anisotropic etching of a tungsten at high selectivity generally requires controlling of a cathode of an etching system at 0xc2x0 C. or lower. Setting of such a low temperature is not a suitable setting for the etching of a titanium-base film. It is therefore difficult to pattern, in the same etching chamber, stacked films of a tungsten film and a titanium-base film with good accuracy without allowing any etch residue to remain.
On the other hand, a titanium-base film useful as a barrier metal can be formed by several processes such as sputtering and CVD (chemical vapor deposition), and its quality varies depending upon the process employed for its formation. Etching of a tungsten film and a titanium-base film in the same chamber may, therefore, result in a situation that a residue does not occur when the barrier metal is formed by a process but does occur when it is formed by another process.
The present invention has been completed to resolve the above-described problem, and has as a first object the provision of a manufacturing process for a semiconductor device, the process always permitting etching of stacked films of a tungsten film and a titanium-base barrier metal with good accuracy without allowing any etch residue to remain irrespective of the forming process of the barrier metal.
The present invention also has as a second object the provision of a semiconductor device manufactured by the above-described manufacturing process.
The above objects of the present invention are achieved by a method for manufacturing a semiconductor device provided with a titanium-base film under a tungsten film. In the method, the tungsten film is etched with a mixed gas of SF6 and Cl2. The titanium-base film is etched with a mixed gas of Cl2 and BCl3.
The above objects of the present invention are also achieved by a semiconductor device manufactured by the method described above.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.